The proposed research is a continuation and extension in new directions of a long-term project aimed at establishing electrophysiological correlates of psychopathology. The ultimate goal is to advance understanding of brain mechanisms involved in psychiatric illness. The electroencephalogram (EEG) and various types of evoked potentials are to be recorded under several experimental conditions, each of which will provide the opportunity to compare functions of the two brain hemispheres. Basic hypotheses propose that psychiatric disorder is associated with deviant patterning and spatial distribution of electrophysiological events; also, that there will be alterations in normal hemispheric asymmetry. The experiments involve: (a) measurement of somatosensory evoked response recovery functions with right and left median nerve stimulation; (b) a vigilance task requiring discrimination between sequences of verbal and nonverbal stimuli; (c) verbal and musical auditory stimuli; (d) checkerboard reversals and checkerboard displays presented separately to each visual field; (e) reaction time responding to checkerboard stimuli presented separately to each visual field. The electrophysiological variables will be analyzed by computer methods to provide indices of intraindividual patterning both with respect to different types of electrical activity and to spatial distribution of these activities. Clinical populations, particularly patients with schizophrenias, affective disorders and personality disorders, will be compared with one another and with nonpatients. Patients will be studied by a variety of test and clinical rating procedures.